1. Field of the Invention
The present invention relates to an information processing apparatus, an information processing method, and a storage medium, and, more particularly to an information processing apparatus which provides an original audio sound when an electronic musical instrument including a MIDI device plays back a file, such as an SMF (Standard MIDI (Musical Instruments Digital Interface) File), at any position other than from its front end. The SMF file here includes, at least, a tone color parameter relating to a tone color and an interval parameter relating to an interval. The present invention also relates to an information processing method and a medium for such an information processing apparatus.
2. Description of the Related Art
Available as a standard format for controlling electronic musical instruments is the MIDI standard. In an electronic keyboard instrument, for example, information in the form of MIDI events is sent to the electronic keyboard instrument in accordance with the MIDI standard. The electronic keyboard instrument is controlled based on the MIDI events so that it generates and outputs an audio sound corresponding to a key indicated by a MIDI event which is pressed.
In the above keyboard instrument, the MIDI event indicating which key to press is used to control the audio signal, and may be called an interval parameter. Besides the interval parameter, the MIDI events include the one for controlling the tone color of an electronic musical instrument (MIDI device), which may be called a tone color a parameter. Available as tone color parameters in the MIDI events are a program change, a control change, and an exclusive message (system exclusive message).
By sending the MIDI signal including the above MIDI events to the MIDI device, the MIDI device generates and outputs a diversity of tone colors and intervals.
The concept "channel" is employed in the MIDI signal format. A plurality of different channels are respectively assigned to a plurality of MIDI devices to independently control the plurality of MIDI devices.
A computer handles the MIDI signal to allow the MIDI device to automatically play. An SMF (Standard MIDI File) is available as a standardized file format to allow the computer to handle the MIDI signal, besides formats unique to individual hardware and software for automatic playing. The SMF holds tempo information and time pattern information, not relating to the MIDI signal, and with the SMF, the MIDI device changes the tempo and time pattern in the middle of a musical performance. The SMF also holds the time information about (effective) time for making effective the tone color parameter and the interval parameter.
As described above, the tempo information and the time pattern information are not the MIDI signal, and unrelated to the tone color. In this specification, however, the tempo information and the time pattern information are included in the tone color parameter for convenience of explanation.
The MIDI standard and SMF are detailed in "MIDI 1.0 Standard" (issued by Japan MIDI Standard Committee).
A tone color parameter to generate a sound having a certain tone color needs to be recorded chronologically earlier than the recorded position of an interval parameter, as a MIDI event in the SMF, a command to generate a corresponding sound. No other particular limitation is specified about the recorded position of the tone color parameter. In the SMF, the tone color parameter and the interval parameter are recorded in a mixed fashion rather than in separate partitions.
When an interval parameter as a command to generate a sound of a predetermined interval (for example, a command for pressing a predetermined key) is recorded at a position corresponding to 10 seconds after the front end of a SMF with the playback starting at the front end of the SMF, the tone color parameter for designating the tone color of the predetermined interval sound (namely, setting the predetermined tone color in the MIDI device) may be recorded anywhere between the front end of the SMF and the position corresponding to 10 seconds after the front end of the SMF.
For example, now, a tone color parameter designating a predetermined tone color is recorded at a position corresponding to 5 seconds after the front end of the SMF. When an access is made in a random fashion, for example, starting the playback at a position corresponding to 6 seconds after the front end of the SMF, the MIDI device generates the sound in accordance with an interval parameter recorded at a position corresponding to 10 seconds after the front end of the SMF. The tone color of the sound corresponds to the tone color parameter that is set to the MIDI device at that position; and does not always correspond to the tone color parameter at a position corresponding to 5 seconds after the start of the SMF. (It is more likely that the tone color of the sound fails to correspond to the position corresponding to 5 seconds after the front end.)
In the SMF, the tone color parameter is not recorded together with the interval parameter as a command for generating a sound. When a playback is made on the SMF on a random-access fashion, music is not always played at an original tone color a composer of the SMF (composer of the music (content) played by the MIDI device) intends to present.